Ebola Vaccines Show Promise in New Study

The first placebo-controlled study of two vaccines against the Ebola virus found they both successfully created a powerful antibody response for a year, suggesting they both could be tools to save lives in a future epidemic of the deadly disease.

The research, by doctors from the U.S. and Liberian governments and elsewhere, was published Wednesday in the New England Journal of Medicine. The study looked at 1,500 patients in Liberia, and took place amid and after the outbreak of Ebola in Liberia from 2014 into 2015.

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Five hundred participants received a vaccine developed by Merck & Co., 500 got one from GlaxoSmithKline PLC, which was based on work by the National Institutes of Health, and 500 received a placebo.

With the Merck vaccine, at one month, 83.7% of patients had developed antibodies to Ebola virus, versus 70.8% with the Glaxo vaccine and a negligible number, 2.8%, in the placebo group. The relationship of antibody responses was similar after 12 months, with 79.5%, 63.5% and 6.8% of patients, respectively, showing antibody response.

There is a "reasonable chance that either of these vaccines would play a role in preventing infection," said H. Clifford Lane, deputy director for clinical research at the National Institute for Allergy and Infectious Diseases and a principal investigator in this study. NIAID is part of the National Institutes of Health. The Liberian Ministry of Health and other researchers also conducted the study.

The West African Ebola outbreak -- the worst in recorded history -- caused an estimated 11,000 deaths amid 25,582 cases in the three nations of Guinea, Liberia and Sierra Leone. The hemorrhagic fever, which can be fatal in half or more cases, spread from West Africa to a handful of cases in Europe and the U.S., including among health care workers. The disease appears and disappears unpredictably in the African forests, and is widely believed to be spread by bats.

In Dr. Lane's view, given previously existing positive evidence from a Guinea study of the Merck vaccine, if doctors in a future epidemic had to choose, it would probably be the one from Merck.

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That Merck vaccine was shown to be "highly efficacious" during the Ebola epidemic in Guinea by World Health Organization doctors writing in The Lancet in December. But the methodology of that study -- including the lack of a placebo group -- raised questions among some scientists about how conclusive those findings were.

A detailed report by the prestigious National Academy of Medicine in April questioned the methodology of the Merck vaccine study in Guinea. It concluded the Merck vaccine "most likely provides some protection" to recipients but that the protection "could in reality be quite low."

One of the authors of that Academy of Medicine report, vaccine specialist and pediatrics professor Kathryn M. Edwards of Vanderbilt University, said the new evidence shows "the safety of the two vaccines is comparable." But she said any comparison of the two vaccines based on the antibody evidence "is a bit undecided" because it is unknown precisely what antibody levels are needed to protect patients.

Merck said the "safety and immunogenicity results observed" in this most recent research "are consistent with what we observed in other studies." GSK said it is too early to know whether the immunity differences between the two vaccines "indicate a clinically meaningful difference." The NIH/GSK vaccine was the focus of a page-one Wall Street Journal article about it and the NIH scientist, Nancy J. Sullivan, who developed it.

The two different studies arose through a kind of scientific war. Several British and other European medical groups, including some who funded the Guinea study of the Merck vaccine, had argued that giving any patients a placebo wasn't ethical in the middle of a raging epidemic. But U.S. government doctors, including leaders of the NIH, said a placebo group was necessary to ensure patients truly got benefit, and weren't harmed, from either a vaccine or a drug.

This current study, in Liberia, was designed to avoid those pitfalls through its classic placebo-controlled design. But it ran into another obstacle: Ebola cases in Liberia began to dwindle early in 2015, and the outbreak there was declared over on May 9 of that year. By the time this work was fully under way, it was too late to see if vaccines actually prevented Ebola sickness and death.

It still was possible, however, to measure patients' immune-systems' response, measured by how many produced significant antibodies to the Ebola virus. Also, vaccine safety could be assessed, and both vaccines appeared safe.

NIH scientists now are evaluating antibody levels out to two years.

The level of serious adverse events was higher in the placebo group than either vaccine group, and "most of the serious adverse events were attributed to malaria," the researchers wrote.